This invention relates to the generation and provision of refrigeration using a turboexpander or reverse Brayton cycle and is especially useful for generating refrigeration at cryogenic temperatures as low as xe2x88x92250 F.
Generally cascade type vapor compression refrigeration cycles, which employ Joule-Thomson valve expansion of a gas to generate refrigeration, are used to provide low temperature refrigeration such as from
xe2x88x9260 F. to xe2x88x92150 F. Typically such vapor compression refrigeration cycles use ozone depleting refrigerants or hazardous refrigerants such as propane or ammonia.
Turboexpander cycles, also known as reverse Brayton cycles, have also been used to supply low temperature refrigeration. Turboexpander cycles are advantageous over cascade type vapor compression cycles in that they are more compact and more reliable than comparable cascade systems which require two or more refrigeration loops, and are also less sensitive to operation away from the design point than are cascade vapor compression cycles. Unfortunately turboexpander refrigeration cycles are limited in their ability to approach the efficiency of such conventional cascade type vapor compression refrigeration cycles.
Accordingly, it is an object of this invention to provide an improved method for providing refrigeration using a turboexpander or reverse Brayton refrigeration cycle.
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention one aspect of which is:
A method for producing refrigeration employing a turboexpander cycle comprising:
(A) compressing a refrigerant mixture comprising at least one component from the group consisting of argon and nitrogen, and at least one component having a normal boiling point within the range of from xe2x88x92100 F. to xe2x88x92260 F.;
(B) cooling the compressed refrigerant mixture;
(C) turboexpanding the cooled compressed refrigerant mixture to provide a two phase turboexpanded refrigerant mixture; and
(D) warming the turboexpanded refrigerant mixture to provide refrigeration to a heat load.
Another aspect of the invention is:
A method for producing refrigeration employing a turboexpander cycle comprising:
(A) compressing a refrigerant mixture comprising at least one component from the group consisting of argon and nitrogen, and at least one component from the group consisting of helium and neon;
(B) cooling the compressed refrigerant mixture;
(C) turboexpanding the cooled compressed refrigerant mixture to provide a two phase turboexpanded refrigerant mixture; and
(D) warming the turboexpanded refrigerant mixture to provide refrigeration to a heat load.
As used herein the term xe2x80x9cindirect heat exchangexe2x80x9d means the bringing of two fluids into heat exchange relation without physical contact or intermixing of the fluids with each other.
As used herein the term xe2x80x9cnormal boiling pointxe2x80x9d means the temperature at atmospheric pressure at which a fluid changes from liquid to a gas.
As used herein the term xe2x80x9cturboexpanderxe2x80x9d means a mechanical device which converts the pressure energy of a fluid into rotational energy. The expanded fluid experiences a reduction in temperature. The rotational energy could be used to drive a compressor wheel or to produce electrical energy.
As used herein the term xe2x80x9cturboexpansionxe2x80x9d means the process of allowing a gas to expand through a turboexpander thus experiencing a reduction in temperature and producing useful work. The expansion of the gas is ideally isentropic.